In microprocessing for manufacturing a semiconductor device or a FPD (Flat Panel Display) using plasma, it is important to control a temperature and a temperature distribution of a substrate as well as a plasma density distribution on a processing target substrate (a semiconductor wafer, a glass substrate or the like). If the temperature control of a substrate is not appropriately performed, uniformity of a reaction on a substrate surface and uniformity of process characteristics may not be secured, resulting in deterioration of a production yield of semiconductor devices or display devices.
Generally, a mounting table or susceptor for mounting thereon a processing target substrate within a chamber of a plasma processing apparatus (especially, a capacitively coupled plasma processing apparatus) has a function as a high frequency electrode for applying a high frequency power into a plasma space; a function as a holder for holding the substrate by electrostatic attraction or the like; and a function as a temperature controller for controlling the substrate at a preset temperature by heat transfer. For the temperature control function, it is required to appropriately adjust a distribution of heat transfer characteristics on the substrate which is dependent on non-uniformity of radiation heat from plasma or a chamber wall or to appropriately adjust a heat distribution which is dependent on a substrate supporting structure.
Conventionally, in order to control a temperature of a top surface of a susceptor (and a temperature of a substrate), there has been widely used a method for forming a coolant passage through which a coolant flows in the susceptor or in a susceptor supporting table and supplying a temperature-controlled coolant into the coolant passage by a chiller device (see, for example, Patent Document 1). However, in this method of using such a chiller mechanism, it has been difficult to rapidly change a temperature of the coolant. Further, since responsiveness in temperature control is low, a temperature variation, a temperature increase or a temperature decrease may not be performed at a high speed.
Recently, in a plasma process, e.g., in a plasma etching process, it is required to successively form multilayer films on a processing target substrate through multi-steps within a single chamber instead of using a conventional method of using multiple chambers. To perform consecutive processes in the single chamber, a temperature of the mounting table needs to be rapidly increased and decreased. In this regard, there has been considered using a heater mechanism capable of accurately controlling a susceptor temperature and a substrate temperature at a high speed by controlling Joule heat generated by a heating member that is installed in a susceptor and generates heat by a power applied thereto.
Meanwhile, in case that a lower electrode high-frequency application type in which a high frequency power supply is connected to the susceptor (lower electrode) is used for a plasma control and, at the same time, the heater mechanism in which the heating member is embedded in the susceptor is used for a temperature control, a part of a high frequency power applied to the susceptor from the high frequency power supply may reach a heater power supply as a noise via the heating member and a heater power feed line, resulting in deterioration of an operation and a performance of the heater power supply. Especially, a high-speed heater power supply capable of being controlled at a high speed performs a switching control or an ON/OFF control with high sensitivity by using a semiconductor switching device such as a SSR (Solid State Relay). Therefore, if a high frequency noise is introduced therein, the heater may suffer an operation failure.
Typically, to prevent this problem, a filter for attenuating or blocking an undesired high frequency noise has been provided on the heater power feed line. This kind of filter needs to have a function of efficiently passing a high current from the heater power supply to the heating member of the susceptor while blocking a passage of a high frequency noise entering the power feed line via the heating member, that is, preventing the high frequency noise from entering the heater power supply by providing a sufficiently high impedance to the high frequency noise, thereby protecting the heater power supply from the high frequency noise and stabilizing plasma within the chamber.
The inventors of the present disclosure have proposed, in Patent Document 2, a plasma processing apparatus in which an air core coil having a sufficiently large inductance is provided in a primary stage of this kind of filter and this air core coil is accommodated within a conductive case installed in the vicinity of a susceptor (typically, below the susceptor).    Patent Document 1: Japanese Patent Laid-Open Publication No. 2006-286733    Patent Document 2: Japanese Patent Laid-Open Publication No. 2008-198902
In the plasma processing apparatus disclosed in Patent Document 2, when a single high frequency power, particularly, a single frequency power of about 13.56 MHz or below is applied to the susceptor (lower electrode), the filter including the air core coil configured as described above may function effectively. Accordingly, a high frequency noise less than about 13.56 MHz can be blocked efficiently and stably on the heater power feed line while a high heater current equal to or greater than about 30 A is allowed to flow in the heater power feed line.
However, it was found out that in case of employing a lower electrode dual frequency application type in which both a high frequency power of a relatively low frequency (typically, about 13.56 MHz or less) for ion attraction and a high frequency power of a relatively high frequency (typically, about 27 MHz or more) for plasma generation are applied to the susceptor, it is difficult to stably and securely block the high frequency noise having a relatively high frequency by using the filter having the above-described configuration. To be specific, if the frequency of the high frequency power for plasma generation is increased (typically, if it is set to be about 60 MHz or higher) in order to obtain high density plasma under a low pressure, an impedance characteristic of the filter for such a high frequency range may become non-uniform. The non-uniformity of the filter characteristic may have adverse effect on reliability and reproducibility of a plasma process, and, thus, a difference in process performance may be caused in a plasma processing apparatus for mass production.
Further, in order to apply high impedance to all of multiple frequencies, a conventional general filter has a configuration in which a plurality of LC parallel resonance circuits having different parallel resonance frequencies is connected in series. With this filter configuration, however, an impedance characteristic may be changed complicatedly because of self-resonance of a coil included in each LC parallel resonance circuit or a mutual interference between the adjacent LC parallel resonance circuits. As a result, reliability and reproducibility of plasma process may be lowered.